<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        p{
            color:green;
            font-size:30px;
        }
        h1{
            color:blue;
            font-size:20px;
        }
        span{
            color:red;
            font-size:30px;
        }
    </style>
</head>
<body>
    <p>你好呀</p>
    <p>见到你</p>
    <h1>我很开心</h1>
    <p>把<span>前端</span>这两个字变成红色</p>
</body>
</html>